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Research article - Peer-reviewed, 2022

Seasonal variation in the coupling of microbial activity and leaf litter decomposition in a boreal stream network

Bastias, Elliot; Sponseller, Ryan A.; Bundschuh, Mirco; Jonsson, Micael


Most stream networks are characterised by spatial and temporal variability in the physico-chemical conditions that regulate microbial processing of particulate organic matter. How these patterns control the turnover of particulate organic matter via altered activity of leaf-associated microbes has rarely been studied in high-latitude landscapes, particularly throughout long (i.e., up to 6 months) ice- and snow-covered periods. We investigated development of fungal biomass, enzyme activity, microbial respiration, and birch leaf litter decomposition from autumn to early summer in 11 nested streams in a boreal catchment that encompass a gradient in wetland (mire) cover. We observed relatively low variability in decomposition rates across the network, despite differences in key physical and chemical variables (e.g. temperature, pH, and dissolved organic carbon [DOC] concentrations) over time and space. Microbial enzymatic activity and respiration were positively related to leaf litter decomposition rates during early stages of decomposition (i.e., up to c. 30% loss of initial ash-free dry mass). Thereafter, variation in microbial activity and respiration was decoupled from leaf litter mass loss, as enzymatic activity and respiration instead became positively related to DOC concentrations and upstream mire (wetland) cover among streams. Our results suggest that leaf-associated microbes increase their reliance on external sources of energy over time. This switch in resource use was more evident in streams with higher DOC concentration, which in boreal landscapes is largely determined by mire cover. Hence, variation in DOC concentration, linked to landscape configuration, or from intensified land use and climate change, could affect how different carbon sources are used by stream microbial communities, with consequences for overall carbon cycling in boreal headwaters.


birch; cellobiohydrolase; extracellular enzyme activity; Krycklan Catchment Study; leaf-use efficiency

Published in

Freshwater Biology
2022, volume: 67, number: 5, pages: 812-827
Publisher: WILEY

Authors' information

Bastias, Elliot
Umea University
Sponseller, Ryan A.
Umea University
University of Koblenz-Landau
Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment
Jonsson, Micael
Umea University

Associated SLU-program

SLU Plant Protection Network

UKÄ Subject classification


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